Automotive vehicles are becoming commonly equipped with antennas that receive and process signals other than traditional AM/FM signals, such as, for example, satellite signals. In particular, antennas relating to satellite digital audio radio services (SDARS), which is broadcast on the 2320-2345 MHz frequency band, is becoming widely available in vehicles as an originally-installed component by an original equipment manufacturer (OEM), or, alternatively, as an after-market component that is installed after the vehicle has been manufactured by the OEM.
SDARS offer a digital radio service covering a large geographic area, such as North America. Satellite-based digital audio radio services generally employ either geo-stationary orbit satellites or highly elliptical orbit satellites that receive up-linked programming, which, in turn, is re-broadcast directly to digital radios in vehicles on the ground that subscribe to the service. SDARS antennas, such as, for example, patch antennas, presently track two satellites at a time. Thus, the mounting location for SDARS patch antennas make antenna reception a sensitive issue with respect to the position of the antenna on a vehicle. As a result, SDARS patch antennas may be mounted exterior to the vehicle, usually on the roof.
SDARS antennas mounted on the roof of a vehicle have typically utilized the metallic roof structure as the antenna ground plane. For such applications, the antenna assembly is coupled to the vehicle roof either with a magnet or with a through-hole fastening structure. A conventional SDARS antenna including a through-hole fastening structure is shown generally at 100 in FIG. 5. The antenna assembly 100 includes an injection molded cover 102, a circuit board assembly 104, a gasket 106, a zinc die-cast case 108, and a first and second plurality of fastening elements 110, 112.
As illustrated, the first plurality of fastening elements 110 secure the circuit board assembly 104 to the zinc die-cast case 108 in a first manufacturing step. The second plurality of fastening elements 112 secure the zinc die-cast case 108 and the gasket 106 to the cover 102 in a second manufacturing step. When assembled, the gasket 106 seals off an opening created by the placement of the cover 102 adjacent a flange 114 of the zinc die-cast case 108 to protect the circuit board assembly 104 from the elements, contaminants, and the like. The zinc die-cast case 108 provides ground coupling between the circuit board assembly 104 and the vehicle roof.
Although adequate for most applications by ensuring good electrical coupling between the vehicle roof and a satellite antenna element 116, which is part of the circuit board assembly 104, such antenna assemblies 100 require many parts, which increase the overall cost of the assembly. Additionally, the first and second plurality of fastening elements 110, 112 require that the antenna assembly 100 be built over multiple assembling steps, which slows production, and hence, the amount of antenna assemblies 100 that may be manufactured. The proposed antenna structure departs from a conventional antenna assembly 100 by eliminating the following components and related processes: 1) fasteners to secure the circuit board assembly to case, 2) fasteners to secure cover to case, and 3) cover to case gasketing.